Furnace



R. R. HARRIS FURNACE Filed March 24, 1939 INVNTOR v. ATTONEY ROMA/NE R. HARE/S AIR Patented Sept. 2, 1941 v V I'CIaim.. My invention relates to furnaces and to the control mechanisms therefor.- vIt isparticularly directedto the automatic burning of, fiuid fuels, although some features ofrnyinvention are useful when solid fuelsare burned.-

The transference of heat from the combustion chamber of a furnace to the circulating medium, which may be either a gas or a liquid, is a' matter of 'difiiculty particularly with the smaller furnaces such as are used in residences. For convenience, the discussion of this problem will hereinafter be confined to thecase where air is used as the circulating medium, that is,. to the hotair type of furnace, although I do .notwish my invention to be limited'to thisparticular type inasmuch as the principles are' applicable to furnaces in which other 'rnedia are heated.

In a hot-air furnace, it is necessarythat the products of combustion be confinediwithina conduit leading to a smokestack. All of the use-.

ful heat must pass through the walls of this conduit; the heat .that remains in the products of combustion and passes up the smoke stack is wasted. For maximum efficiency, the temperature of the gases passing up the smoke stack must approach that ,ofthe air being heated. This requires that the aforesaid conduit; be long and of a substantial area. However, when said conduit is made long, the difficulty encountered that too much draft is required .to draw the products of'combustion' through it. Although sufiicient draft. may readily be provided by means of .a smokestack, this form'of.

draft is not effective until thegases within the conduit become hot, and said gasescannot be heated without draft." This impasse tends to cause smoking of the furnace'while it is heating up. i The foregoing exposition is elemental in the heating art, and ithasv heretofore been com-' when the fire is first started. Thereafter, when the gases in the combustion chamber and in the smokestack have become sufficiently hot to provide a good draft. the aforesaid by-passv is closed by means of a check-valve and the products of combustion then pass through the entire conduit and therein give up as much as possible of their.

sensible heat. An object of my invention isto provide a thermostat for automatically operating the aforesaid check valve, none heretofore being available that were sufliciently simple and The requirecheap for use on small furnaces.

ES PATIENT -OFFICE] f 2,254,481 '1 a f n f I1 v Romaine R.- Harris, Portland, .Qreg. Application-March 24, 193$,iSerialiNb. 263,862: i

mentsfof a satisfactory thermostat'fo'r this purpose are, discussed more fully hereinafter.

The length of, conduit through which it'jhas heretofore been deemed feasible to pass the hot gases of a furnace has been limited. by the danger of said conduit bursting due to aimild explosion within the firebox. v Particularly, when oil is burned, a condition occurs in which the firebox becomes partially filled withfan unburned 1o mixture of airand fuel. This condition may be caused by a momentary interruption of the fuel supply, resulting in a relatively thin'stratum of pure air separating the. flamefrom the succeeding combustible air-fuel mixture. When the: 15 flame is subsequently propagated jbaek through said stratum of air, the 'combustible'mixture,

burns rapidly and produces a sufficientlyhigh momentary pressure to rupture itscontaining conduit if the'length of said conduit be too great. A further object of my invention isto.

provide a by-pass and a check valve thei'efor at all times is required. The 'inertia'of the valve must be sufficiently low so that the valve can? open 'quii k y; otherwise the conduit will burst in much the same way that algim'barrel does" ifit is fired while obstructed by mud. Q

Afurther object of my invention is to provide' 1 'a thermostatic control for a furnace wherein theeifect'of the ,fldifierential 'expansionof two metals when theirjtemperature changes is augmented by maintaininga differential tempera ture between said metals, the metal having the higher temperature coefficient of expansion be 40 mg maintained at the'higher' temperature. I attain's'aid object by so arranging'the metal elements. whosedifferential expansion" is to be utilized that the one having the-lower coefficient of expansion is exposed to adraft of relatively cool air whilebeing protected from the'actuating heat-su p r. f j 5 Other objects and advantages of my invention will be described with reference to the accom panying drawing in 'which- Fig. 1 is a fragmentary vertical sectional view of a. furnace embodying my invention; 7 Fig. 2 is a horizontal sectiOnQtakensubstantially along the line 2--2 of Fig. 1; Y f

Fig. 3 is a vertical section taken along the 55 line 3-3 in Fig. 1;

which will relieve the aforesaid pressure'due to a mild explosion, thus permitting thefuse 'of'a; longer conduit which 'will'resul-t ma more com- V plete. transfer of heat from' the' combustionf chamber to the circulating air; For this purpose, a light weight .valve that free to open j 'flow throughthe longeracond Fig. 4'is an enlarged irriunwntary-detail view of one end of the thermostat shown in. Fig. 1;

Fig. 5 is an enlarged fragmentary detail view of the other end of said thermostat.

An oil burner adapted'for use with a furnace embodying my invention is described more fully on a yoke. 25 in which pin 26 is oui'nzilvd. Pin 25 serves as a pivotfor lever 21. A clamp 28 press fitted on the end of tube 2 is pivotally secured .to said lever by pin 29. I propose to make tube of some materiahsuch as brass, which has a high temperature coefficient of expansion, and to make rod lfl'oi'some material, such as in my copending application for United States. patent entitled Liquid "fuel burning apparatus,

itto say'here that the magnitude of the flame produced by saidburner is adjustable by means of valve Said burner is adapted to produce a v flame in combustion chamber -3. 'Iwoalterna,- :15

tivepaths for the products of combustion are 7 provided between said chamber and 'sinokestacl: 4. :First, a direct path through risers 5 and .lnanifold 6, said path. being available whenfvalve 7 steel, which hasa lower coeflicient.

- to close by its own weight.

said tube and rodjare heated equally, they will react, uponleveiv 21, to retract rod. l8, which is pivotally secured :to said lever, to

allow valve 1 However. I do not propose that tube 2| and rod ,20 shall beheated equally; I prefer to arrange these elements in such away that/said tube will I be heatdtto a higher temperature than said rod, 1 thus augmenting vthe'aioresaid differential elon- 1 is open. Second, when said valve is closedfth e hot gases will go f rom'rise rsj 5 to braneh pipes 8, thence to main pipes 9 ,flthence" tol iSefjl m} thence to smokestack ,4 'Thu'sj combustion chamber 3 is connectedto, smokestack] 4 by" a: 1 branched; conduit comprising risers pipes 6, main pipes 9,'and riser lfl. I

Removable plates 1H may, if desired, be provided tojfacilita'te cleani ng soot' or ashes fr'oni main pipes 9. Pipes I: are adaptedtoconductj heat from the furnace to the roomsfto be heated; and returnp pffi to return said airth'ereto 'I f desired,lagfan orblow'er'migh't be'used' to cir-j i a h? gation." To this'en'd, I provideholes-3flin fitting 23 to admit cool air from outside the furnace to tube 24., Rod within said tube is thus protectedfrorrithe heat of the furnace by said tube, and it "is' cooled by' said" air; tfTo provide draft to draw said air through-said tube, I preferto inclinethe latter at'a substantial angle: Rod-J8 andlug l fl maybe'rnade oi soni'e material having" I a low coefficient of expansion, if desired.

Clamp ZB -Jmay be provided {with an ear 3t adapted't'o engage lever 32 operatively connected 7 some; 33.,1 Said rack engagespinion 34 fixedly culate said air'in which case 'a single ducti'hightil be, interposed between said pipes lzand the furf pace to accommodate said ran, andfiresh outside" airxnay be: admitted to the system; by apD jQpria tef means; However, Ifdeemit advisable to' arrange sald return pipesnjearthe'bottorh of the furnace casingj H ,in, iord er that th'ejrelatively ,cool" air therefrom shall be directed against main pipejsjS.

If the he'at is'ito befthoroughly extracted from the", product'sQof combustion, itf rnust bedone t gradually and,the'final poition,of jjthe conduit securedto valved: Said valve is adapted to regulate the new of liquid fuel to burner I, when said pinion is rotated;and the direction of rota tion of saidvalve is such'that expansion of tube '21 will close it; thus reducing the flame as the temperature within the furnace increasesfi Said valve [may be -'designed and, adjusted to reduce said jfiame to a'negligible' sizewhen said ternperature reaches a predetermined value:

h 'a'ioresaid thermostatic device, including tube 24 and rod 20;is adapted to exert an enorimous for'ce'to operate valves land 2, said forcei must bathe coolest; ltliri 'a'y -beadjvisable to linesaidfitjrhbustion c'hambergwithFireerete' l5,'ff or s omesiinilar heat resistari material, to prevent} ill ihterfere's'onfe fwhatwith thefflowmf negate thecirculating airi Accordingly, the remainder of th'econduitjmustcorrosion thereof and thi be 'of'substantial length to'iprovidejjor saidjfiow;

As mentioned, valve T "is adapted, whenIcloseif 't'o div'ert'ithe products of 'cornbustionffrom th'e directitaa to the, smokesta bejixed'ly secured to shaft itislfree to c us n hc 'fj Seidvmveg y u ch a iwiay that' 'it willntenid totbejclosed bygravity, and sq may "irig open j to relievej undue pressure? in theI'hombu stion chamber; as, hereinbe f0re"de- I of" rod a use apted 't'o'fbear, the longitudinal thrust oisaid rodppeningvalve T. ,7

. {A lug l9 extends .o'jtsi'de eas ng?! (and there supports rthermostat. rod 0,, -which'jinay, if de;

sired; be provided'jiwith a; hou iierp adap ed t be drawn against said lugj; by niit i22engagiingi the, threadedend or sa'idirod. Sa id lugextends I within the furn'ace' casing, and is provided :Ylith a holeinear'its" inner end' which serves as a bean ing for shaft 16.] An janiiular' fitting 23 is press .fltted on rod llna r ithe end thereof, and said fitting is adapted ,to" carrytube Hfwhichmay; if

' desired, be pressfitted into said fittir'ig, The end of rod opposite lug, I Qfcari'ies threaded "there;

" to said 'i'urr ace being limited only by the' strength 'of the mate-1 rialsus'edi However, this force is e'fifectivepver oriIy a irelatively 'sniall distance, which may be r" magnified by levers, as described: {I deem-it 1m; portanjt that saidfleversbefso arranged that'ajj mrmm oi lo'st' motion is 'permi'tted," thus con-:

'servirigthe effective thermal expansion. I

V I claim.

{a} rufea'e comprisingla'iconduit 'for the prod-j uctsj." of combustion," a bypass for, a portion "of said conduitpa valve 'ionf sa'id by-pa'ss, said valve thermostat pteditojholdsaid valve open when 1 said; furnace fisffcold, said' f thermostat being": adapted progressively'to allow" said 'valv'e'to close when said Iurnageis heated' abovea 'predeter "mined ternper t re, j saidthermostati-l'being 'adaptedTprogressiv' 'toreducetlie 'iu'el supply latter -ii ereasefbeybi d a predetermined value,

,said thermostat ,cornprising an 'outer element having a; relatively high itemperature. coeflicientor expansion and an nner element having a relatively lowj temperature coeflicient' of expansion,-

said inner element being {ventilated to maintain 1 its temperature'lowerythan 'that of said ,:outer' element. saidouter elementconsisting of an inclined tube'open at each end, each of said ends being outside said-furnace. J 1

U mMAmaRlmRhs. Q,

Thus, when e'n' 'the' temperature 9 of the; 

